1. Field of the Invention
This invention relates to two stroke internal combustion engines and in particular to such engines fuelled by liquified or compressed fuel gas.
2. Description of the Prior Art
Two stroke or two cycle engines are well known and conventionally use liquid petroleum as a fuel and the moving components in the crankcase are lubricated by oil. Most commonly the oil is premixed with the liquid fuel at a typical ratio of 1 to 50 by weight and is introduced into the combustion chamber via a carburettor. Liquified fuel gas usually comprises propane, butane and other gaseous hydrocarbons and is well known as a fuel for heating and lighting as well as for internal combustion engines. In this specification the term liquified fuel gas refers to combustible gases that are in the gaseous state at ambient temperature and atmosphere pressure, but which under pressure are normally stored in the liquid state. Their source is usually from naturally occurring gas or oil fields. The term fuel gas also includes combustible gases synthetically made or made from the degradation of waste matter. The term also includes generally combustible gases, including hydrogen. In this specification the term compressed fuel gas refers to combustible gases stored under greater than atmospheric pressure. Despite its widespread availability and lower retail price, liquified or compressed fuel gas has hitherto been confined to four stroke internal combustion engines. Previously it has not been found that liquified fuel gas can be satisfactorily used as a fuel for two stroke engines.